Pharmaceutical compositions for gastrointestinal drug delivery

ABSTRACT

A novel pharmaceutical composition, which comprises a therapeutically effective amount of active principle(s) or a pharmaceutically acceptable salt or enantiomer or polymorph thereof, optionally one or more release controlling agent(s) and pharmaceutical acceptable excipient(s) thereof, wherein the composition is formulated to increase the residence time of the said pharmaceutical composition and/or active principle(s) in the gastrointestinal tract. A novel pharmaceutical composition comprising at least two entities wherein one entity is an immediate release/fast release and the other is controlled release. A pharmaceutical composition comprising at least two entities wherein one entity is an immediate release/fast release and the other is bioadhesive. A pharmaceutical composition comprising: at least two entities wherein one entity is controlled release and the other is bioadhesive All the three compositions are formulated to increase the residence time of active principle(s) in the gastrointestinal tract. A multilayered composition with active in a layer which provides immediate release or controlled release of active principles and layer providing increased residence time in the GI tract.

FIELD OF THE INVENTION

The present invention relates to pharmaceutical formulations of activeprinciple(s) for providing increased residence time in thegastrointestinal tract and the process of preparing them.

BACKGROUND OF THE INVENTION

A number of drugs act in the gastrointestinal tract. Oral drugadministration is by far the most preferable route for takingmedications. However, on oral administration, normal or pathologicalstomach voiding and intestinal peristaltic movements limit the time forwhich a drug-releasing dosage form remains in the gastrointestinal tractor at the required site of action. Specifically, during pathologicalconditions such as diarrhea, peristaltic movement of the GI Tract isincreased. Therefore, GI transit time of dosage forms is lesser thannormal. Hence conventional dosage forms have shorter residence time atthe site of absorption or at required site of action and need to bedosed frequently in order to be therapeutically effective. A rationalapproach to solve this problem and to enhance bioavailability andimprove pharmacokinetic and pharmacodynamic profiles is to retain thedrug reservoir above its absorption area or the site of action, and torelease the drug in a controlled manner, for a prolonged period of time.However, controlling the GI residence time is a challenge. We havesurprisingly found that it is possible to extend the GI residence timeof non-systemic locally acting drugs when administered in controlledrelease mucoadhesive dosage forms.

Drugs like (i) carbamazepine (an antiepileptic), furosemide (adiuretic), metoprolol (a beta blocker) and acyclovir (an antiviral)benefit from prolonged presence at or near the locus of absorption interms of their bioavailability characteristics including drugs that actspecifically on the gastrointestinal tract (e.g. 5-aminosalicylic acid)or which are absorbed most efficiently within the intestine or colon(e.g. peptides or proteins such as insulin, interferon, calcitonin,endorphins, human growth hormone, and various hormone growth factors).

Known bioadhesive solid dosage forms are described, for example, inGB-2,042,888 (Teijin). A slow release pharmaceutical preparation to beused adhering to the mucosa of the oral cavity (buccal) or nasal cavitycomprising an active ingredient, 50 to 95% of a cellulose ether and 50to 5% of a high molecular weight crosslinked polyacrylic acid(carboxyvinyl polymer, carbomer, carbopol).

U.S. Pat. No. 6,303,147 (Janssen) describes a bioadhesive pharmaceuticalcomposition comprising a pharmaceutically effective amount of an activeingredient, from 80% to 98.8% (w/w) pre-gelatinized starch, and from 1%to 10% (w/w) of a hydrophilic matrix forming polymer, characterized inthat the composition further comprises from 0.2% to 5% (w/w)alkaliC16-22 alkyl fumarate as a lubricant.

U.S. Pat. No. 6,306,789 (Reckitt Benckiser Healthcare) describesbioadhesive granules of carbomer and in particular to such granulescontaining pharmaceutical active agents suitable for sustained releaseinto the gastrointestinal tract or for targeted delivery to thegastrointestinal mucosa.

U.S. Pat. No. 5,900,247 (Adir et compagnie) describes the bioadhesivefilms or patches characterized by the use: of a polymer (A) composed ofone or a number of vinyl acetate/polyvinylpyrrolidone copolymers.

U.S. Pat. No. 5,472,704 (Recordati S. A.) describe compositioncharacterized by plurality of small-size units capable of ensuring agradual release of the active ingredient they contain the units beingcoated with a bioadhesive polymer layer. The composition makes itpossible to keep the release controlling function separate from thefunction providing bioadhesion.

WO 2006/031420 (Spherics) describes bioadhesive formulation includes amultilayered core enveloped by a bioadhesive coating.

OBJECTS OF THE INVENTION

An object o the invention is to provide a novel pharmaceuticalcomposition, which comprises a therapeutically effective amount ofactive principle(s) or a pharmaceutically acceptable salt or enantiomeror polymorph thereof, optionally one or more controlled release agent(s)and pharmaceutical acceptable excipient(s) thereof, wherein thecomposition is formulated to increase the residence time of the saidpharmaceutical composition and/or active principle(s) in thegastrointestinal tract.

Another object of the invention is to provide a novel pharmaceuticalcomposition comprising: at least two entities wherein one entity is animmediate release or fast release and the other is controlled releasewherein the composition is formulated to increase the residence time ofactive principle(s) in the gastrointestinal tract.

Another object of the invention is to provide a novel pharmaceuticalcomposition comprising: at least two entities wherein one entity is animmediate release or fast release and the other is bioadhesive whereinthe composition is formulated to increase the residence time of activeprinciple(s) in the gastrointestinal tract.

Another object of the invention is to provide a novel pharmaceuticalcomposition comprising: at least two entities wherein one entity iscontrolled release and the other is bioadhesive wherein the compositionis formulated to increase the residence time of active principle(s) inthe gastrointestinal tract.

Another object of the invention is to provide a novel pharmaceuticalcomposition in the form of a multilayer tablet comprising, a) at leastone layer which comprises, a therapeutically effective amount of activeprinciple(s) or a pharmaceutically acceptable salt or enantiomer orpolymorph thereof, pharmaceutically acceptable excipient(s); wherein thesaid layer provides a immediate or fast release of active principle(s);and b) at least another layer which provides increased residence time ofthe dosage form in the gastrointestinal tract.

Another object of the invention is to provide a novel pharmaceuticalcomposition in the form of a multilayer tablet comprising, a) at leastone layer which comprises, a therapeutically effective amount of activeprinciple(s) or a pharmaceutically acceptable salt or enantiomer orpolymorph thereof, pharmaceutically acceptable excipient(s); wherein thesaid layer provides a controlled release of active principle(s); and b)at least another layer which provides increased residence time of thedosage form in the gastrointestinal tract.

Another object of the invention is to provide a novel pharmaceuticalcomposition in the form of a multilayer tablet comprising, a) at leastone layer which comprises, a therapeutically effective amount of activeprinciple(s) or a pharmaceutically acceptable salt or enantiomer orpolymorph thereof, pharmaceutically acceptable excipient(s); and b) atleast one layer comprising another or same active principle(s) whereinlayer (b) provides increased residence time of the dosage form in thegastrointestinal tract.

Another object of the invention is to provide a novel pharmaceuticalcomposition in the form of a multilayer tablet comprising, a) at leastone layer which comprises, a therapeutically effective amount of activeprinciple(s) or a pharmaceutically acceptable salt or enantiomer orpolymorph thereof, pharmaceutically acceptable excipient(s); wherein thesaid layer provides a immediate or fast release of active principle(s);and b) at least one layer comprising another or same active principle(s)wherein layer (b) provides residence time of the dosage form in thegastrointestinal tract.

Another object of the invention is to provide a novel pharmaceuticalcomposition in the form of a multilayer tablet comprising, a) at leastone layer which comprises, a therapeutically effective amount of activeprinciple(s) or a pharmaceutically acceptable salt or enantiomer orpolymorph thereof, pharmaceutically acceptable excipient(s); wherein thesaid layer provides controlled release of active principle(s); and b) atleast one layer comprising another or same active principle(s) whereinlayer (b) provides increased residence time of the dosage form in thegastrointestinal tract.

Another object of the invention is to provide a novel pharmaceuticalcomposition in the form of a multilayer tablet comprising, a) at leastone layer which comprises, a therapeutically effective amount of activeprinciple(s) or a pharmaceutically acceptable salt or enantiomer orpolymorph thereof, pharmaceutically acceptable excipient(s); wherein thesaid layer provides a immediate or fast release of active principle(s);and b) at least one layer comprising another or same active principle(s)wherein layer (b) provides controlled and/or increased residence time ofthe dosage form in the gastrointestinal tract.

Yet another object of the invention is to provide a novel pharmaceuticalcomposition comprising a therapeutically effective amount of activeprinciple(s) or a pharmaceutically acceptable salt or enantiomer orpolymorph thereof, optionally one or more release controlling agent(s)and pharmaceutical acceptable excipient(s) thereof, wherein thecomposition is formulated to increase the residence time of the saidpharmaceutical composition and/or active principle(s) in thegastrointestinal tract, having an adhesive strength, measured as a forceof detachment, of at least 100 mN when measured using advanced forcegauge equipment (manufactured by Mecmesin, West Sussex, England).

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a novel pharmaceutical composition,which comprises a therapeutically effective amount of activeprinciple(s) or a pharmaceutically acceptable salt or enantiomer orpolymorph thereof, optionally one or more controlled release agent(s)and pharmaceutical acceptable excipient(s) thereof, wherein thecomposition is formulated to increase the residence time of the saidpharmaceutical composition and/or active principle(s) in thegastrointestinal tract. The pharmaceutical composition according to theinvention can remain attached for desired period of time to theepithelial surface or to the mucosal membrane of the gastrointestinaltract. Since many drug compounds are absorbed exclusively in the smallintestine or in a limited segment of the GI tract, it would therefore bebeneficial to develop dosage forms such as sustained release dosageforms, which remains in the stomach and/or in the proximal and/or in thedistal portion of the intestine for an extended period of time. Thecompositions of the present invention are preferably administered asonce-a day. It can be administered twice a day or once a week.

Preferred group of drugs that could benefit from retained and controlledor immediate release in the gastrointestinal tract are those meant forthe treatment of pathologies located in the stomach, the duodenum or thesmall intestine or colon.

The terms “active principle,” “drug” “active agent” “active” and“pharmacologically active agent” are used interchangeably herein torefer to a chemical material or compound which, when administered to anorganism (human or animal, generally human) induces a desiredpharmacologic effect. In the context of the present invention the activeprinciples are selected from the group comprising anti-infectives,penicillins, cephalosporins, cyclines, beta-lactamase inhibitors,aminosides, quinolones, nitroimidazoles, sulfamides, antihistaminics,antiallergics, anesthetics, steroidal or non-steroidalanti-inflammatories, analgesics with local or systemic effect,antispasmodics, anticancers, diuretics, beta-blockers,antihypertensives, antianginals, antiarrhythmics, vasodilators,bradycardic agents, calcium inhibitors, sedatives, cardiotonics,antifungals, antiulceratives, vasotonics, vasoprotectants,anti-ischemics, antiemetics, anticoagulants, antithrombotics,immunosuppressants, immunomodulators, antivirals, antiretrovirals,antidiabetics, hypolipidemics, agents for combating obesity,anticonvulsants, hypnotics, antiparkinsonians, antimigraines,neuroleptics, anxiolytics, antidepressants, psychostimulants, agents forpromoting memory, bronchodilators, antitussives, agents for combatingosteoporosis, peptides, hormones, steroids, enzymes, enzyme inhibitors,proteins, melatonergic agonists or antagonists, hormonal agents, acidityreducing agents (e.g., buffering agents such as potassium phosphatedibasic, calcium carbonate, sodium bicarbonate, sodium and potassiumhydroxide, etc.) or combinations thereof.

The preferred active agents that can be used in conjunction with thepresent invention include rifaximin, vancomycin, mesalamine,cholestesamine, balasalazide, sulfasalazine etc.

“Therapeutically effective amount” means that the amount of activeagent, which halts or reduces the progress of the condition beingtreated or which otherwise completely or partly cures or actspalliatively on the condition. A person skilled in the art can easilydetermine such an amount by routine experimentation and with an undueburden.

“Controlled release,” means drug delivery system releasing the drug at apredetermined rate, locally or systemically, for a specified period oftime. Controlled release can be used interchangeably with prolongedrelease, programmed release, timed release, extended release, sustainedrelease and other such dosage forms.

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.

By “pharmaceutically acceptable” is meant a carrier comprised of amaterial that is not biologically or otherwise undesirable.

“Entities” or “Entity” can be interchangeably used with granules,pellets, beads, minitablets and the like.

In an embodiment prolonged gastrointestinal residence can be obtained byusing oral mucoadhesive formulation and/or by reducing gastrointestinalmotility or a combination of one or more techniques.

In another embodiment, the gastroretentivity of the dosage formcomposition might also be achieved by delaying the gastric emptying timesuch as by administration of food.

The term “mucoadhesive” can be used interchangeably with “bioadhesive”and is defined as a natural or synthetic component, includingmacromolecules, polymers, and oligomers, or mixtures thereof, that canadhere to a subject's mucous membrane.

“Bioadhesion” or “mucoadhesion” is defined as the ability of a materialto adhere to a biological tissue for an extended period of time.Bioadhesion is one solution to the problem of inadequate residence timeresulting from stomach emptying and intestinal peristalsis, and fromdisplacement by ciliary movement. For sufficient bioadhesion to occur,an intimate contact must exist between the bioadhesive and the receptortissue, the bioadhesive must penetrate into the crevice of the tissuesurface and/or mucus, and mechanical, electrostatic, or chemical bondsmust form. Bioadhesive properties of polymers are affected by both thenature of the polymer and by the nature of the surrounding media.

“Residence time” is the time required for a pharmaceutical dosage formto transit through the stomach to the rectum i.e. the pharmaceuticaldosage forms of the invention may have an increased retention time inthe stomach and/or small and/or large intestine, or in the area of thegastrointestinal tract that absorbs the drug contained in thepharmaceutical dosage form. For example, pharmaceutical dosage forms ofthe invention can be retained in the small intestine (or one or twoportions thereof, selected from the duodenum, the jejunum and theileum). These pharmaceutical dosage forms as a whole, may include abioadhesive polymeric coating that is applied to at least one surface ofthe dosage form.

Examples of mucoadhesives for use in the embodiments disclosed hereininclude, but are not limited to, natural, semisynthetic and syntheticpolymers.

Natural polymers include proteins (e.g., hydrophilic proteins), such aspectine, zein, modified zein, casein, gelatin, gluten, serum albumin, orcollagen, chitosan, oligosaccharides and polysaccharides such ascellulose, dextrans, tamarind seed polysaccharide, gellan, carrageenan,xanthan gum, gum Arabic; hyaluronic acid, polyhyaluronic acid, alginicacid, sodium alginate.

When the bioadhesive polymer is a synthetic polymer, the syntheticpolymer is typically selected from polyamides, polycarbonates,polyalkylenes, polyalkylene glycols, polyalkylene oxides, polyalkyleneterephthalates, polyvinyl alcohols, polyvinyl ethers, polyvinyl esters,polyvinyl halides, polyvinylpyrrolidone, polyglycolides, polysiloxanes,polyurethanes, polystyrene, polymers of acrylic and methacrylic esters,polylactides, poly(butyric acid), poly(valeric acid),poly(lactide-co-glycolide), polyanhydrides, polyorthoesters,poly(fumaric acid), poly(maleic acid), and blends and copolymers ormixtures thereof.

Other polymers suitable for use in the invention include, but are notlimited to, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose,hydroxypropylmethyl cellulose, hydroxybutylmethyl cellulose, celluloseacetate, cellulose propionate, cellulose acetate butyrate, celluloseacetate phthalate, carboxymethyl cellulose, cellulose triacetate,cellulose sulfate sodium salt, poly(methyl methacrylate), poly(ethylmethacrylate), poly(butyl methacrylate), poly(isobutyl methacrylate),poly(hexyl methacrylate), poly(isodecyl methacrylate), poly(laurylmethacrylate), poly(phenyl methacrylate), poly(methyl acrylate),poly(isopropyl acrylate), poly(isobutyl acrylate), poly(octadecylacrylate) polyethylene, polypropylene, poly(ethylene glycol),poly(ethylene oxide), poly(ethylene terephthalate), polyvinyl acetate),polyvinyl chloride, polystyrene, polyvinyl pyrrolidone, andpolyvinylphenol. Polylactides, polyglycolides and copolymers thereof,poly(ethylene terephthalate), poly(butyric acid), poly(valeric acid),poly(lactide-co-caprolactone), poly[lactide-co-glycolide],polyanhydrides (e.g., poly(adipic anhydride)), polyorthoesters, blendsand copolymers thereof.

Another group of polymers suitable for use as bioadhesive polymers arepolymers having a hydrophobic backbone with at least one hydrophobicgroup pendant from the backbone. Suitable hydrophobic groups are groupsthat are generally non-polar. Examples of such hydrophobic groupsinclude alkyl, alkenyl and alkynyl groups. Preferably, the hydrophobicgroups are selected to not interfere and instead to enhance thebioadhesiveness of the polymers.

A further group of polymers suitable for use as bioadhesive polymers arepolymers having a hydrophobic backbone with at least one hydrophilicgroup pendant from the backbone. Suitable hydrophilic groups includegroups that are capable of hydrogen bonding or electrostatically bondingto another functional group. Example of such hydrophilic groups includenegatively charged groups such as carboxylic acids, sulfonic acids andphosphonic acids, positively charged groups such as (protonated) aminesand neutral, polar groups such as amides and imines.

Preferably, the hydrophilic groups are selected to not interfere andinstead to enhance the bioadhesiveness of the polymers. In embodimentsof the present invention, a pharmaceutical composition comprises anactive agent and at least one swellable polymer.

Swellable polymers include, but are not limited to, a crosslinkedpoly(acrylic acid), a poly(alkylene oxide), a polyvinyl alcohol), apolyvinyl pyrrolidone); a polyurethane hydrogel, a maleic anhydridepolymer, such as a maleic anhydride copolymer, a cellulose polymer, apolysaccharide, starch, and starch based polymers.

Polymers can be modified by increasing the number of carboxylic groupsaccessible during biodegradation, or on the polymer surface. Thepolymers can also be modified by binding amino groups to the polymer.The polymers can be modified using any of a number of different couplingchemistries available in the art to covalently attach ligand moleculeswith bioadhesive properties to the surface-exposed molecules of thepolymeric microspheres.

Lectins can be covalently attached to polymers to render them targetspecific to the mucin and mucosal cell layer. The attachment of anypositively charged ligand, such as polyethyleneimine or polylysine, to apolymer may improve bioadhesion due to the electrostatic attraction ofthe cationic groups coating the beads to the net negative charge of themucus. The mucopolysaccharides and mucoproteins of the mucin layer,especially the sialic acid residues, are responsible for the negativecharge coating. Any ligand with a high binding affinity for mucin couldalso be covalently linked to most polymers with the appropriatechemistry, such as with carbodiimidazole (CDI), and be expected toinfluence the binding to the gut. For example, polyclonal antibodiesraised against components of mucin or else intact mucin, when covalentlycoupled to a polymer, would provide for increased bioadhesion.Similarly, antibodies directed against specific cell surface receptorsexposed on the lumenal surface of the intestinal tract would increasethe residence time when coupled to polymers using the appropriatechemistry. The ligand affinity need not be based only on electrostaticcharge, but other useful physical parameters such as solubility in mucinor specific affinity to carbohydrate groups.

The covalent attachment of any of the natural components of mucin ineither pure or partially purified form to the polymers generallyincreases the solubility of the polymer in the mucin layer. The list ofuseful ligands include but are not limited to the following: sialicacid, neuraminic acid, n-acetyl-neuraminic acid, n-glycolylneuraminicacid, 4-acetyl-n-acetylneuraminic acid, diacetyl-n-acetylneuraminicacid, glucuronic acid, iduronic acid, galactose, glucose, mannose,fucose, any of the partially purified fractions prepared by chemicaltreatment of naturally occurring mucin, e.g., mucoproteins,mucopolysaccharides and mucopolysaccharide-protein complexes, andantibodies immunoreactive against proteins or sugar structure on themucosal surface.

The attachment of polyamino acids containing extra pendant carboxylicacid side groups, such as polyaspartic acid and polyglutamic acid, mayalso increase bioadhesiveness. The polyamino chains would increasebioadhesion by means of chain entanglement in mucin strands as well asby increased carboxylic charge.

A bioadhesive controlled release pharmaceutical dosage form of theinvention can have one or more coatings such as enteric coating,controlled release coating, film coating, sugar coating, bioadhesivecoating. In one example, the additional coating prevents the bioadhesivedosage form from contacting the mouth or esophagus. In another example,the coating remains intact until reaching the small intestine (e.g., anenteric coating). Examples of coatings include methylmethacrylates,zein, cellulose acetate, cellulose phthalate, HMPC, sugars, entericpolymers, gelatin and shellac. Premature exposure of a bioadhesive layeror dissolution of a pharmaceutical dosage form in the mouth can beprevented with a layer or coating of hydrophilic polymers such as HPMCor gelatin.

Coating agents which are useful in the coating process, include, but arenot limited to, polysaccharides such as maltodextrin, alkyl cellulosessuch as methyl or ethyl cellulose, hydroxyalkylcelluloses (e.g.hydroxypropylcellulose or hydroxypropylmethylcelluloses);polyvinylpyrrolidone, acacia, corn, sucrose, gelatin, shellac, celluloseacetate pthalate, lipids, synthetic resins, acrylic polymers, opadry,polyvinyl alcohol, copolymers of vinylpyrrolidone and vinyl acetate(e.g. marketed under the brand name of Plasdone) and polymers based onmethacrylic acid such as those marketed under the brand name ofEudragit. These may be applied from aqueous or non-aqueous systems orcombinations of aqueous and non-aqueous systems as appropriate.

The bioadhesive polymers discussed above can be mixed with one or moreplasticizers or thermoplastic polymers. Such agents typically increasethe strength and/or reduce the brittleness of polymeric coatings. Theplasticizers include dibutyl sebacate, polyethylene glycol, triethylcitrate, dibutyl adipate, dibutyl fumarate, diethyl phthalate, ethyleneoxide-propylene oxide block copolymers and di(sec-butyl) fumarate,thermoplastic polymers include polyesters, poly(caprolactone),polylactide, poly(lactide-co-glycolide), methyl methacrylate, celluloseand derivatives thereof such as ethyl cellulose, cellulose acetate andhydroxypropyl methyl cellulose and large molecular weightpolyanhydrides. Antitacking agents such as talc, stearic acid, magnesiumstearate and colloidal silicon dioxide and the like. Surfactants such aspolysorbates and sodium lauryl sulphate and opacifying agents such astitanium dioxide and the like. All these excipients can be used atlevels well known to the persons skilled in the art.

A pharmaceutical dosage form can have one or more coatings in additionto the bioadhesive polymeric coating, e.g., covering the surface of thebioadhesive coating. These coatings and their thickness can, forexample, be used to control where in the gastrointestinal tract thebioadhesive coating becomes exposed.

Pharmaceutical dosage forms of the invention can be coated by a widevariety of methods. Suitable methods include compression coating,coating in a fluidized bed or a pan and hot melt (extrusion) coating.Such methods are well known to those skilled in the art.

Also suitable are rupturable coating systems, e.g., Pulsincap, that useosmotic forces of swelling from hydrophilic polymers to rupture entericmembranes to reveal underlying bioadhesive dosage form.

Alternately, non-permeable coatings of insoluble polymers, e.g.,cellulose acetate, ethylcellulose, can be used as enteric coatings fordelayed/modified release (DR/MR) by inclusion of soluble pore formers inthe coating, e.g., PEG, PVA, sugars, salts, detergents, triethylcitrate, triacetin, etc.

Also, coatings of polymers that are susceptible to enzymatic cleavage bycolonic bacteria are another means of ensuring release to distal ileumand ascending colon. Materials such as calcium pectinate can be appliedas coatings to tablets and multiparticulates and disintegrate in thelower gastrointestinal tract, due to bacterial action. Calcium pectinatecapsules for encapsulation of bioadhesive multiparticulates are alsoavailable.

The pharmaceutically acceptable excipients, are selected from the groupcomprising binders, diluents, lubricants, surfactants and glidants.

Binder is one or more selected from the group comprising carbohydrateslike celluloses their derivatives; starches; gums; polyvinylpyrrolidone,povidone, syrup, polyethylene oxide, polyacryl amide, poly-N-vinylamide, sodium carboxymethyl cellulose, polyethylene glycol, gelatin,polyethylene oxide, poly propylene glycol, tragacanth, alginic acid,combinations thereof.

Diluent is one or more selected from the group comprising carbohydrates,derivatives of carbohydrates, polyols, sugar alcohols, carbonate,sulphate or phosphate salts of inorganic metals or mixtures thereof.

Lubricants is one or more selected from the group comprising Magnesium,Aluminium, Zinc or Calcium stearate, polyethylene glycol, mineral oil,sodium stearyl fumarate, stearic acid, hydrogenated vegetable oil,glyceryl behenate, glyceryl palmitostearate, glyceryl stearate,cornstarch, talc, calcium silicate, magnesium silicate, colloidalsilicon dioxide, silicon hydrogel, and mixtures thereof.

Surfactant can be selected from ionic or non-ionic or zwitterionicsurfactants.

Glidant is one or more selected from the group comprising silicondioxide, colloidal silica, powdered cellulose, talc, tribasic calciumphosphate and mixtures thereof.

The novel pharmaceutical composition of the present invention canfurther have solubilizing agents. Solubilizing agents include but arenot limited to surfactants, cyclodextrin and its derivatives, lipophilicsubstances or any combination thereof.

Unlimiting examples of surfactants include water-soluble or waterdispersible nonionic, semi-polar nonionic, anionic, cationic,amphoteric, or zwitterionic surface-active agents; or any combinationthereof.

Other solubilizing agents include vitamin E and its derivatives;monohydric alcohol esters such as trialkyl citrates, lactones and loweralcohol fatty acid esters; nitrogen-containing solvents; phospholipids;glycerol acetates such as acetin, diacetin and triacetin; glycerol fattyacid esters such as mono-, di- and triglycerides and acetylated mono-and diglycerides; propylene glycol esters; ethylene glycol esters; andcombinations thereof.

In another embodiment of the novel pharmaceutical composition of thepresent invention can further have stabilizing agents. Stabilizingagents include but are not limited to catalysts, antioxidants,adsorbents, absorbents, buffers, chelating and sequestering agents,carbonate salt of said amino acid is present as either the group I or IIalkali or alkali earth metal salt and combinations thereof.

Pharmaceutical compositions of the invention is but not limited topowders, pellets, beads, granules, tablets, compacts, sustained releaseformulations, capsules, microcapsules, tablets in capsules, tablets intablets, microspheres, shear form particles, floss, and flakes ormixtures thereof. Tablets include single layered tablets, multilayeredtablets, mini tablets, bioadhesive tablets, caplets, matrix tablets,tablet within a tablet, mucoadhesive tablets. Sustained release isformulation include but are not limited to matrix type controlledrelease, membrane diffusion controlled release, site targeted,osmotically controlled release, pH dependent delayed release, timedrelease, pulsatile release, hydrodynamic balanced system; powders,pellets, beads, granules for suspension.

Multi-layer tablets comprises a first, a second or/and a third layer,where each layer includes one or more excipients and optionally one ormore drug.

At least one layer of the tablet includes a hydrophobic excipient orhydrophilic excipient or combinations thereof.

Exemplary hydrophobic excipients include celluloses, particularlycellulose acetate and ethyl cellulose, stearic acid, magnesium stearate,glycerol monostearate, fatty acids and salts thereof, monoglycerides,diglycerides, triglycerides, oil, colloidal silicon dioxide and talc.

Such tablets include one excipient present in an amount sufficient to beat least partially rate-controlling with respect to release of the drugfrom the tablet.

For tablets containing two or more drugs, the drugs can both be presentin one or more layers or the different drugs are present in separatelayers.

For drugs requiring absorption in the stomach and upper small intestineand/or topical delivery to these sites, particularly drugs with narrowabsorption windows, bioadhesive, gastroretentive drug delivery systemsare the option of choice. Drugs requiring absorption or topical deliveryonly in the small intestine, enteric-coated, bioadhesive drug deliverysystems are preferred. For drugs requiring absorption or topicaldelivery only in the lower small intestine and colon enteric-coated,bioadhesive drug delivery systems are preferred.

Multi-layer or gradient tablets can be assembled in several differentways.

In one embodiment, the tablet comprises at least one controlled releaselayer and one bioadhesive layer, where in controlled release layercomprises one or more pharmaceutical polymers and/or pharmaceuticalexcipients, one or more drugs.

In one embodiment, the tablet comprises at least one controlled releaselayer and one bioadhesive layer, each comprising one or morepharmaceutical polymers and/or pharmaceutical excipients, optionally oneor more drugs. Such tablets can also be used to commence release ofdifferent drugs at different times, by inclusion of different drugs inseparate layers.

In one embodiment, the tablet comprises at least one solid inner layerand two solid outer layers, each comprising one or more pharmaceuticalpolymers and/or pharmaceutical excipients. The inner layer comprises oneor more active ingredient and rate-controlling polymer. The two solidouter layers are bioadhesive.

In one embodiment, the tablet comprises at least one solid inner layerand two solid outer layers, each comprising one or more drugs and one ormore pharmaceutical polymers and/or pharmaceutical excipients. Suchtablets can also be used to commence release of different drugs atdifferent times, by inclusion of different drugs in separate layers.

In another embodiment, the multi-layer tablet consists of a solid innerlayer and two solid outer layers, each comprising a drug and one or morepharmaceutical polymers or pharmaceutical excipients, wherein at leastone polymer or excipient is hydrophobic.

In an embodiment, the composition of the present invention comprises atleast two fractions wherein one fraction is an immediate release or fastrelease fraction providing an immediate release of the active agent andthe other fraction is an extended release fraction that releases theactive agent over extended periods of time.

One or more layers of the tablet can contain permeation enhancers toprovide permeability enhancement of drugs through mucosal lining of thegastrointestinal tract (GIT). An absorption enhancer facilitates theuptake of a drug across the gastrointestinal epithelium. Absorptionenhancers include compounds that improve the ability of a drug to besolubilized in the aqueous environment in which it is originallyreleased and/or in the lipophilic environment of the mucous layer liningof the intestinal walls.

In still another embodiment, the multi-layer tablet is enteric coated.Optionally Eudragit FS 30D or other suitable polymer may be incorporatedin coating composition to retard the release of the drug to ensure drugrelease in the colon.

It is also an object of the invention to provide the a pharmaceuticalcomposition, wherein the said composition is formulated by compressingor compacting powder, granules, pellets, beads, shear form particles,floss, or the like, or combinations thereof. The said composition of thepresent invention may be filled into capsule or made into a capsule,wherein the said capsule is in the form of a hard gelatin capsule orsoft gelatin capsule.

It is also an object of the present invention to provide pharmaceuticalcomposition wherein the composition is in the form of a compressed orcompacted multiparticulate composition comprising a blend of one or moretypes of particles, granules, pellets, beads, compacts, minitablets,shear form particles, floss, or the like, or combinations thereof,having different release characteristics or a multiparticulatecomposition made into a capsule or filled into a capsule.

It is also an object of the present invention to provide apharmaceutical composition of active principle(s), wherein thecomposition is in the sustained release form, timed release form,pulsatile release form, prolonged release form, extended release form ordelayed release form, or a combination thereof. The composition can alsoadditionally comprise an immediate release composition.

The compositions can be prepared in an easy and cost effective manner.

The foregoing examples are illustrative embodiments of the invention andare merely exemplary. A person skilled in the art may make variationsand modifications without deviating from the spirit and scope of theinvention. All such modifications and variations are intended to beincluded within the scope of the invention.

EXAMPLES Example 1

Ingredients % w/w Active 20 Sodium Alginate 40 Water QS Calcium chloride15 Polyethylene oxide (PEO) 10 Sodium Carboxymethyl Cellulose (NaCMC) 11Colloidal silicon dioxide  2 Magnesium stearate  2Procedure

-   i) Sodium alginate is suspended in water and active was suspended in    this colloidal solution.-   ii) Calcium Chloride is dissolved in water and kept aside.-   iii) Add step (i) into step (ii) dropwise to make beads under    stirring, further filter the solution to separate the beads and dry    the beads.-   iv) Mix the dried beads with xanthan gum and sodium alginate.-   v) Lubricate the beads of step (iv) with magnesium stearate and fill    into capsules or sachets or filled in bottles with sweetening and    flavouring agents as a powder for suspension.

Example 2

Ingredients % w/w Active 25 Diluents (e.g., Mannitol or DCP or MCC) 40PEO 20 Polyvinyl Pyrolidone (PVP) 10 Isopropyl Alcohol (IPA) QSMagnesium Stearate  2 Colloidal silicon dioxide  2Procedure:

-   i) Sift Active, Diluent, PVP and PEO through a suitable seive.-   ii) Granulate blend of step (i) with IPA.-   iii) Dry the granules of step (ii) and sift through a suitable    seive.-   iv) Lubricate the granules of step (iii) with magnesium stearate.-   v) The bioadhesive granules of step (iv) can be further compressed    into tablets using suitable diluents and lubricants or filled into    capsules or sachets or filled into bottle with sweetening and    flavouring agents as a powder for suspension.

Example 3

Ingredients % w/w Active 20 Diluent (MCC/DCP) 40 Sodium Alginate 10Xanthan gum 10 NaCMC 15 Sodium bicarbonate 4 Sodium Lauryl Sulphate(SLS) 1 Water QSProcedure:

-   Spheronization-   i) Mix all the ingredients except sodium bicarbonate in a blender.-   ii) Dissolve sodium bicarbonate in water.-   iii) Granulate (ii) with (i)-   iv) Wet mass of step (ii) is passed through Extruder and further    spheronized to get the round pellets

The pellets can be filled into capsules, sachets or filled in bottleswith sweetening and flavouring agents as a powder for suspension orcompressed into tablets.

Example 4

Ingredients % w/w Active 30 Dliuents (e.g., Mannitol or DCP or MCC) 30HPMC 10 Poloxamer 10 PEO 10 Colloidal silicon dioxide 5 Magnesiumstearate 5Procedure:

-   i) Sift Active, Diluent, HPMC, Poloxamer and PEO through a suitable    seive-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.-   v) The blend is then compressed into tablets

Example 5

Ingredients % W/W Active 30 Diluents (e.g. Mannitol or DCP or MCC) 30HPMC 10 Poloxamer 10 Sodium Alginate 10 Colloidal silicon dioxide 5Magnesium Stearate 5Procedure:

-   i) Active, Diluents, HPMC, Poloxamer and sodium alginate are sifted    through a suitable seive.-   ii) Step (i) is dry blended in a blender.-   iii) Lubricants are sifted through a suitable seive and mixed with    step (ii).-   iv) Blend of step (iii) is then compressed into mini tablets.-   v) These mini tablets can be filled into capsules

Example 6

B) First and Third Layer

Ingredients % W/W Active 5 HPMC 35 PEO 40 Polycarbophil 15 CollodialSilicon Dioxide 3 Magnesium Stearate 2Procedure:

-   i) Sift active, HPMC, PEO and Polycarbophil through a suitable    seive.-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.-   v) Divide (iv) into equal portions for first and third layer.    A) Middle Layer

Ingredients % W/W Active 70 Diluents (E.g., Mannitol or DCP or MCC) 16HPMC 10 Colloidal silicon dioxide 2 Magnesium Stearate 2Procedure

-   i) Sift active, diluent and HPMC through a suitable seive-   ii) dry blend (i) in an blender/granulation can be done using IPA or    water.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.

Blends of A and B are compressed into trilayer tablets

Example 7

Ingredients % W/W Active 20 Diluents (e.g. Mannitol or DCP or MCC) 25HPMC 10 PEO 15 Vitamin E TPGS* 20 Colloidal silicon dioxide 3 MagnesiumStearate 2 *D-alpha-tocopheryl polyethylene glycol 1000 succinateProcedure

-   i) Mix active with Vitamin E TGPS at 70° C., cool to room    temperature.-   ii) Pulverize (i) using a suitable sieve-   iii) Mix (ii) with all other excipients except the lubricants in a    blender.-   iv) Mix (iii) with magnesium stearate and colloidal silicon dioxide    in a blender.-   v) The blend is then compressed into tablets.

Example 8

B) First and Third Layer

Ingredients % W/W Active 5 HPMC 30 PEO 40 Polyvinyl alcohol (PVA) 10 SLS10 Collodial Silicon Dioxide 3 Magnesium Stearate 2Procedure:

-   i) Sift active, HPMC, PEO, PVA and SLS through a suitable seive.-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.-   v) Divide (iv) into equal portions for first and third layer.    A) Middle layer

Ingredients % W/W Active 70 Diluents (E.g., Mannitol or DCP or MCC) 15HPMC 10 Colloidal silicon dioxide 3 Magnesium Stearate 2Procedure

-   i) Sift active, diluent and HPMC through a suitable seive-   ii) dry blend (i) in a blender/granulation can be done using IPA or    water.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.

Blends of A and B are compressed into trilayer tablets

Example 9

Ingredients % w/w Active 30 Dliuents (e.g., Mannitol or DCP or MCC) 30HPMC 15 PEO 25 Colloidal silicon dioxide 3 Magnesium stearate 2Methylene chloride QS IPA QSProcedure:

-   i) Sift Active, Diluent, HPMC and PEO through a suitable seive.-   ii) dry blend (i) in a blender.-   iii) Granulate (ii) with IPA:Methylene chloride.-   iv) Dry (iii) in fluid bed dryer.-   v) Granules obtained in (iv) are sifted through a suitable seive.-   vi) Sift Colloidal silicon dioxide and magnesium stearate through    suitable seive-   vii) Lubricate (v) with (vi) in a blender.-   v) The blend is then compressed into tablets

Example 10

Ingredients % w/w Active 40 Dliuents (e.g., Mannitol or DCP or MCC) 10HPMC 20 PEO 20 NaCMC 5 Colloidal silicon dioxide 3 Magnesium stearate 2Procedure

-   i) Sift Active, Diluent, HPMC, NaCMC and PEO through a suitable    seive-   ii) dry blend (i) in a blender.-   iii) Sift Colloidal silicon dioxide and magnesium stearate through a    suiatble seive-   iv) Add half quantity of (iii) to (ii) and mix in a blender.-   v) Compact blend of (iv) using a roller compactor at a pressure.-   vi) sift (v) through suitable seive to obtain granules-   vii) Mix remaining quantity of (iii) and (vi) in a blender.-   viii) Blend of (vii) is compressed into tablets.

Example 11

Ingredients % w/w Active 50 Dliuents (e.g., Mannitol or DCP or MCC) 15HPMC 10 PEO 15 Guar gum 5 Colloidal silicon dioxide 3 Magnesium stearate2 Water QSProcedure:

-   i) Sift active, diluent, HPMC, guar gum and PEO through a suitable    seive-   ii) dry blend (i) in a blender.-   iii) Granulate (ii) with water and dry the wet mass in fluid bed    dryer.-   iv) Granules obtained in (iii) are sifted through a suitable seive.-   v) Sift Colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   vi) Lubricate (iv) with (v).-   vii) Blend of step (vi) is then compressed into tablets.

Example 12

A) First Layer

Ingredients % w/w Active 40 Dliuents (e.g., Mannitol or DCP or MCC) 25HPMC 30 Colloidal silicon dioxide 3 Magnesium stearate 2 IPA QSMethylene chloride QS

-   i) Sift active, diluent and HPMC through a suitable sieve and mix in    a blender.-   iii) Granulate (i) with IPA:methylene chloride, and dry the wet mass    in a fluid bed dryer.-   iii) Granules of (iii) passed through a suitable sieve.-   iv) Sift colloidal silicon dioxide and magnesium stearate through a    suitable seive-   v) Lubricate (iv) with (v).    B) Second layer

Ingredients % w/w HPMC 30 PEO 35 Dliuents (e.g., Mannitol or 25 DCP orMCC) Colloidal silicon dioxide 5 Magnesium stearate 5

-   i) Sift HPMC, diluent and PEO through a suitable seive.-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.

Compress both A and B to form bilayer tablet.

Example 13

B) First and Third Layer

Ingredients % W/W HPMC 40 Xanthan gum 20 Polycarbophil 25 Colloidalsilicon dioxide 5 Magnesium stearate 5Procedure:

-   i) Sift HPMC, Xanthan gum and Polycarbophil through a suitable    seive.-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.    A) Middle layer

Ingredients % W/W Active 50 Diluents (e.g., Mannitol or DCP or MCC) 15HPMC 10 Colloidal silicon dioxide 7 Magnesium stearate 3 Water QS

-   i) Sift active, diluent, and HPMC through a suitable selve-   ii) dry blend (i) in a blender.-   iii) Granulate (i) with (ii) and dry the wet mass in fluid bed dryer-   iv) Granules obtained in (iii) are sifted through a suitable seive.-   v) Sift Colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   vi) Lubricate (iv) with (v).-   vii) Blend of A and B is then compressed into trilayered tablet.

Example 14

B) First and Third Layer

Ingredients % W/W HPMC 40 Xanthan gum 20 PEO 30 Colloidal silicondioxide 5 Magnesium stearate 5Procedure:

-   i) Sift HPMC, Xanthan gum and PEO through a suiatble seive-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.    A) Middle Layer

Ingredients % W/W Active 40 Diluents (e.g., Mannitol or DCP or MCC) 10HPMC 15 Colloidal silicon dioxide 3 Magnesium stearate 2 IPA QSMethylene chloride QSProcedure:

-   i) Sift active, diluent, and HPMC through a suitable seive.-   ii) dry blend (i) in a blender.-   iii) Granulate (ii) with IPA:methylene chloride and dry the wet mass    in fluid bed dryer.-   iv) Granules obtained in (iii) are sifted through a suitable seive.-   v) Sift Colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   vi) Lubricate (iv) with (v).-   viii) Blend A and B are then compressed into trilayer tablet.

Example 15

A) First Layer

Ingredients % w/w Active 35 HPMC 15 PEO 20 Dliuents (e.g., Mannitol or25 DCP or MCC) Colloidal silicon dioxide 2 Magnesium stearate 3 Water QSProcedure

-   i) Sift active, diluent, HPMC and PEO through a suitable sieve and    mix in a blender.-   ii) granulate (i) with water and dry the wet mass in a fluid bed    dryer.-   iii) granules of (ii) passed through a suitable sieve.-   iv) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive-   v) lubricate (iv) with (v).    B) Second Layer

Ingredients % w/w HPMC 40 PEO 35 Carbomer 15 Colloidal silicon dioxide 5Magnesium stearate 5

-   i) Sift HPMC, carbomer and PEO through a suitable seive-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.

Blends of A and B are then compressed into bilayer tablets.

Example 16

A) First Layer

Ingredients % w/w Active 30 HPMC 30 Xanthan gum 10 Dliuents (e.g.,Mannitol or 25 DCP or MCC) Colloidal silicon dioxide 3 Magnesiumstearate 2

-   i) Sift active, diluent, HPMC and xanthan gum through a suitable    seive-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.    B) Second Layer

Ingredients % w/w HPMC 35 PEO 35 Diluents (e.g., Mannitol or DCP or MCC)20 Colloidal silicon dioxide 5 Magnesium stearate 5

-   i) Sift HPMC, diluent and PEO through a suitable seive-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.

Blends of A and B are then compressed into bilayer tablets.

Example 17

B) First and Third Layer

Ingredients % W/W HPMC 40 Xanthan gum 20 Polycarbophil 25 Colloidalsilicon dioxide 5 Magnesium stearate 5Procedure:

-   i) Sift HPMC, Xanthan gum and Polycarbophil through a suitable seive-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.    A) Middle layer

Ingredients % W/W Active 40 Diluents (e.g., Mannitol or DCP or MCC) 20HPMC 15 PEO 15 Colloidal silicon dioxide 7 Magnesium stearate 3 Water QS

-   i) Sift active, diluent, HPMC and PEO through a suitable seive.-   ii) dry blend (i) in a blender.-   iii) Granulate (ii) with water and dry the wet mass in fluid bed    dryer.-   iv) Granules obtained in (iii) are sifted through a suitable seive.-   v) Sift Colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   vi) Lubricate (iv) with (v).-   vii) Blend of A and B is then compressed into trilayered tablets.

Example 18

A) First Layer

Ingredients % w/w Active 70 HPMC 5 Diluents (e.g., Mannitol or 21 DCP orMCC) Colloidal silicon dioxide 2 Magnesium stearate 2Procedure:

-   i) Sift active, diluent, HPMC and diluent through a suitable seive.-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.    B) Second Layer

Ingredients % w/w Active 40 HPMC 35 Diluents (e.g., Mannitol or 20 DCPor MCC) Colloidal silicon dioxide 3 Magnesium stearate 2

-   i) Sift active, diluent, HPMC and diluent through a suitable seive.-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.    C) Third Layer

Ingredients % w/w HPMC 40 Xanthan gum 20 PEO 30 Colloidal silicondioxide 5 Magnesium stearate 5

-   i) Sift xanthan gum, PEO and HPMC through a suitable seive.-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.

Blend of A, B and C is then compressed into trilayered tablets.

Example 19

A) First Layer

Ingredients % w/w Active 50 HPMC 20 Carbomer 10 Dliuents (e.g., Mannitolor DCP or MCC) 15 Colloidal silicon dioxide 2 Magnesium stearate 3Procedure:

-   i) Sift active, HPMC, carbomer and diluents through a suitable seive-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.    B) Second Layer

Ingredients % w/w HPMC 30 PEO 40 Xanthan gum 20 Colloidal silicondioxide 2 Magnesium stearate 3

-   i) Sift HPMC, xanthan gum and PEO through a suitable seive-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.

Blends of A and B are then compressed into bilayer tablets.

Example 20

Ingredients % W/W Active 2 Diluents (e.g. Mannitol or DCP or MCC) 15HPMC 30 PEO 45 Stabilizing agent 5 Colloidal silicon dioxide 2 MagnesiumStearate 1Procedure:

-   i) Active, Diluents, HPMC, stabilizing agent and PEO are sifted    through a suitable seive.-   ii) Step (i) is dry blended in a blender.-   iii)Lubricants are sifted through a suitable seive and mixed with    step (ii).-   iv) Blend of step (iii) is then compressed into tablets.-   HPMC=Hydroxy propyl methyl cellulose-   PEO=Polyethyeleneoxide-   DCP=Dicalcium phosphate-   MCC=Microcrystalline cellulose-   IPA=Iso Propyl alcohol    Determination of Bioadhesion

Bioadhesion was determined by tensiometric method. For thedetermination, an advanced force gauge equipment (mfg. by Mecmesin, WestSussex, England) was used. Freshly excised Sheep intestinal tissue wastaken and stored in a Tyrode solution at 4° C. until used for theexperiment. The tissue was cut into pieces (3×4 cm) and mounted on theglass slide and tightened with a thread. 0.5 ml Phosphate bufferedsaline (PBS) was placed on the tissue. The bioadhesive tablet preparedas in examples 1 to 6, was placed on this tissue and another 0.5 ml PBSwas placed on the tablet. A glass slide with a 10 g weight was placed onthe tablet and it was allowed to hydrate for 10 min., 30 min., 60 min.,840 and 960 min. At the specific time interval, the hydrated tabletalong with slide was mounted on the stage of the bioadhesion apparatus.Probe was then lowered at fixed speed of 0.2 mm/sec. and upper slide wasattached to the hook of the probe by means of a thread. The peakdetachment force was considered as the bioadhesive force. The forcerequired to separate the tablet from biological substrate was recordedin mN as demonstrated in accompanying FIG. 1.

Formula 1: Sr. No. Ingredients % w/w 1. PEO 48.86 2. MCC 48.86 3.colloidal silicon 1.36 dioxide 4. Magnesium 0.91 stearate

-   i) Sift MCC and PEO through a suitable seive.-   ii) dry blend (i) in a blender.-   iii) sift colloidal silicon dioxide and magnesium stearate through a    suitable seive.-   iv) Lubricate (ii) with (iii) in a blender.

Compress into a tablet.

Formula 2: Sr. No. Ingredients % w/w 1. HPMC 48.86 2. MCC 48.86 3.Colloidal silicon 1.36 dioxide 5. Magnesium 0.91 stearate

Formula 3: Sr. No. Ingredients % w/w 1. PEO 48.86 2. Xanthan gum 48.863. colloidal silicon dioxide 1.36 5. Magnesium stearate 0.91

Formula 4: S. No. Ingredients % w/w 1. Xanthan Gum 48.86 2. MCC 48.86 3.Colloidal silicon dioxide 1.36 4. Magnesium Stearate 0.91

Formula 5: S. No. Ingredients % w/w 1. PEO 48.86 2. Sodium CMC 48.86 3.Colloidal silicon dioxide 1.36 4. Magnesium Stearate 0.91

Formula 6: S. No. Ingredients % w/w 1. Sodium CMC 48.86 2. MCC 48.86 3.Colloidal silicon dioxide 1.36 4. Magnesium Stearate 0.91

All tablets are prepared as explained in Formula 1.

The invention claimed is:
 1. An oral multilayer tablet comprising: afirst layer comprising a pharmaceutical composition comprising rifaximinor a pharmaceutically acceptable salt thereof and that is configured forimmediate or fast release of the rifaximin or salt thereof; and a secondlayer comprising the rifaximin or salt thereof and a polymer havingaffinity for gastrointestinal mucosa, wherein the polymer adheres to thegastrointestinal mucosa and provides increased residence time of thetablet in the gastrointestinal tract by bioadhesion which is independentof food effect, wherein the composition has an adhesive strength,measured as a force of detachment, of at least 1000 mN in 30 minutes,and wherein bioadhesion is provided for a period greater than 0.5 hour.2. The multilayer tablet of claim 1, comprising at least one activeprinciple in addition to rifaximin.